Base isolation device for structure

ABSTRACT

A base isolation device for a structure capable of efficiently and effectively suppressing the vibration of a structural body in surface outside direction, wherein a tension member having on overall length longer than an interval between support points provided on the structural body at a specified interval is disposed between the support points, one end parts of first link pieces are rotatably connected midway to the tension member directly or through rigid members, one end parts of second link pieces are rotatably connected to the structural body, the other end parts of the first link pieces are rotatably connected to the other end parts of the second link pieces, and an energizing member providing a tension to the tension member by energizing the first link piece and the second link piece and a damping member operated by the rotation of the first link piece and the second link piece are installed between the structural body forming the structure and connection parts between the first link pieces and the second link pieces.

This application is a national filing pursuant to 35 U.S.C Section 371based on PCT/JP02/13630, filed Dec. 26, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a base isolation device for a structure, andmore particularly to a base isolation device for a structure that isapplied to a structure having structural members such as slabs inelevated freeways, elevated railway tracks, or bridge constructions, andsuppresses vibration in the out-of-plane direction of the structuralmembers.

Moreover, the invention can also be applied to a base isolation devicethat suppresses vibration in the out-of-plane direction of structuralmembers of an inclined roof, or structural-support members of avertically placed glass curtain wall.

2. Description of the Related Art

In recent years, various measures have been employed for suppressingdamage such as collapse or failure of structures comprising structuralelements such as the slabs in elevated freeways, elevated railwaytracks, or bridge constructions due to vertical vibration of thestructural members that occurs during traffic vibration or anearthquake, and one of the measures that has been proposed is the baseisolation device shown in FIG. 5.

The base isolation device that is indicated by reference number 1 inthis FIG. 5, is applied to a floor slab 3 that is arranged horizontallyas a structural member that is supported by a plurality of bridgesupports 2, for example, and underneath the floor slab 3, in about thecenter between the bridge supports 2, an elastic member 4 comprising aspring or the like, and a damping member 5 comprising an oil damper orthe like are suspended such that they are parallel with each other, anda weight member 6 is attached to the bottom section of the elasticmember 4 and damping member 5.

In this prior base isolation device 1 constructed in this way, whenvibration in the out-of-plane direction (in the vertical direction inthe example shown in the FIG. 5) occurs in the floor slab 3, thevertical vibration of the floor slab 3 is suppressed by damping therelative motion between the floor slab 3 and the weight member 6 by theelastic member 4 and damping member 5.

In this kind of prior art, there still remain the following problemsthat must be improved.

In other words, in the prior art described above, in order toefficiently suppress the vertical vibration in the floor slab 3, it isnecessary to properly set the elastic coefficient of the elastic member4 and the damping coefficient of the damping member 5 in accordance tothe characteristic natural frequency of the floor slab 3, however, inorder to do this, there is a problem in that the range capable ofobtaining an effective base isolation function is narrow, and thesetting of which is difficult.

Moreover, the weight member 6 is more effective the heavier it is,however, in an actual structure, it was difficult to attach a weightthat was 10% the weight of the entire structure.

Furthermore, since the weight member 6 acts only in the direction ofgravitational acceleration, installing this prior base isolation devicein the structural members of an inclined roof, or the structural-supportmembers of a vertically placed glass curtain wall was impossible.

SUMMARY OF THE INVENTION

Taking these prior problems into consideration, the object of thisinvention is to provide a base isolation device for a structure that iscapable of effectively suppressing vibration in the out-of-planedirection of the structural members of a structure.

In order to accomplish the object described above, the base isolationdevice for a structure according to the first embodiment of theinvention is a base isolation device for a structure that suppressesvibration in the out-of-plane direction of a structural member of thestructure and comprises: In the base isolation device for a structureaccording to the seventh embodiment of the invention, the damping memberof any one of the described embodiments is an active damper, andtogether with locating a sensor for detecting shaking on said structuralmember, a controller is installed that adjusts the operation of saidactive damper based on the detection signal from the sensor.

In the base isolation device for a structure according to the eighthembodiment of the invention, the sensor of the seventh embodiment is anacceleration sensor.

In the base isolation device for a structure according to the ninthembodiment of the invention, the sensor of the seventh embodiment is adisplacement sensor.

In the base isolation device for a structure according to the tenthembodiment of the invention, the sensor of the seventh embodiment is avelocity sensor.

In the base isolation device for a structure according to the eleventhembodiment of the invention, the damping member of any one of thedescribed embodiments is a viscoelastic member or elasto-plastic member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing the main parts of a first embodiment ofthe present invention.

FIG. 2 is a plane view showing the main parts of a first embodiment ofthe present invention.

FIG. 3 is an enlarged view of the main parts for explaining theoperation of a first embodiment of the present invention.

FIG. 4 is a front view showing another embodiment of the presentinvention.

FIG. 5 is a front view of the main parts of a prior example.

FIG. 6 is a front view showing another embodiment of the presentinvention.

FIG. 7 is a front view showing another embodiment of the presentinvention.

FIG. 8A and FIG. 8B are front views showing examples of modifications tothe present invention.

FIG. 9 is a plane view showing an example of a modification to thepresent invention.

FIG. 10 is a front view showing an example of a modification to thepresent invention.

FIG. 11 is a front view showing an example of a modification to thepresent invention.

FIG. 12 is a front view showing an example of a modification to thepresent invention.

FIG. 13A, FIG. 13B and FIG. 13C are front views showing examples ofmodifications to the present invention.

FIG. 14 is a front view showing an example of a modification to thepresent invention.

FIG. 15 is a front view showing an example of a modification to thepresent invention.

FIG. 16 is a front view showing an example of a modification to thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of the present invention will be explained below withreference to FIG. 1 to FIG. 3.

The base isolation device 10 for a structure of this embodiment, whichis indicated by the reference number 10 in FIG. 1, is applied to a floorslab 12, which is a structural member that is supported by a pluralityof bridge supports 11, and is basically constructed by comprising:support points 13 that are located underneath the floor slab 12 andseparated by a specified space (in this embodiment, they are located onadjacent bridge supports 11), and where a tension member 14 is placed inbetween these support points 13 having an overall length that is longerthan the space, and where first link pieces 15 are connected to pointsalong the tension member 14 such that they can rotate freely, and secondlink pieces 16 that are connected between the first link pieces 15 andthe floor slab 12 such that they can rotate freely; an energizing member17 that applies tension to the tension member 14 by energizing the firstlink pieces 15 and second link pieces 16 between the connections of thefirst link pieces 15 and second link pieces 16 and the structural memberof the structure (floor slab 12 in this embodiment); and a dampingmember 18 that is operated by the rotation of the first link pieces 15and second link pieces 16.

Also, there is an added mass 25 located in the connections 21 betweenthe first link pieces 15 and second link pieces 16.

To explain these in more detail, in this embodiment, rope is used as thetension member 14 and both ends are fastened to the support points 13that are located on the bridge supports 11.

In this embodiment, the first link pieces 15 and second link pieces 16are located underneath the floor slab 12, and are located at two placesseparated by a space midway in the space between adjacent bridgesupports 11 in the length direction of the tension member 14, and oneend of each of the first link pieces 15 is connected to the tensionmember 14 by way of a pin 19 such that it can rotate freely, and one endof each of the second link pieces 16 is connected to the bottom of thefloor slab 12 by way of a pin 20 such that it can rotate freely.

Moreover, the other end of each of the first link pieces 15 and secondlink pieces 16 are connected together by way of a pin 21 such that theycan rotate freely, as well as an added mass 25 is added, andfurthermore, the first link pieces 15 are formed such that they areshorter than the second link pieces 16, and the pins 21 of theconnections between the first link pieces 15 and second link pieces 16are located on the inside between both pins 19 of the connectionsbetween the first link pieces 15 and the tension members 14.

Furthermore, in this embodiment, as shown in FIG. 2, base isolationdevices 10 are mounted between a pair of bridge supports 11 that arelocated such that they are parallel in the plane direction of the floorslab 12, and the two pins 21 that connect the first link pieces 15 andsecond link pieces 16 of each base isolation device 10 are shared, andthey (pins 21) are made sufficiently heavy in order that they can takeon the role of the added mass 25, and a pair of energizing members 17are located in parallel between these pins 21, and furthermore a dampingmember 18 is located between these energizing members 17 and isconnected to both pins 21.

Also, both energizing members 17 are constructed using tension springs,and by energizing both pins 21 in a direction such that they approacheach other, and by energizing the pins 19, which are the connections ofeach of the first link pieces 15 with the tension members 14, in adirection such that they become separated from the floor slab 12,tension is applied to the tension members 14 and keeps the tensionmembers 14 in a state of tension.

Next, the operation of the base isolation device 10 of this embodimentconstructed in this way will be explained.

When an earthquake or the like occurs, the floor slab 12 vibrates in thevertical direction, which is the out-of-plane direction of the floorslab 12, such that the bridge supports 11 are fixed ends, and the middlesection bends.

Moreover, as shown in FIG. 3, when the floor slab 12 bends downward fromthe normal state as shown by the single-dot dashed line to the stateshown by the double-dot dashed line, for example, each of the pins 20moves downward together with the floor slab 12, and each of the secondlink pieces 16 that are connected to the pins 20 receive a force thatalso similarly moves them downward.

However, by keeping the tension members 14 in a state of tension, thepositions of the pins 19, which are one of the connections with thefirst link pieces 15, are restricted, so as the second link pieces 16move downward as described above, the second link pieces 16 are rotatedaround the center of the pins 19.

The direction of rotation of the first link pieces 15 is in a directionsuch that the pins 21, which are the connections with the second linkpieces 16, move away from each other, and inertial force acts togetherwith the gravitational force on the added mass 25 connected directly tothe pins 21.

As a result, both of the energizing members 17 located between both pins21 expand and together with keeping the tension members 14 in a state oftension, the damping member 18 is expanded, and the damping functionoccurs.

From this, the vertical vibration of the floor slab 12 described above,is converted to motion of the added mass 25, and due to the occurrenceof the damping function, the vertical vibration of the floor slab 12 issuppressed.

On the other hand, as shown in FIG. 3, when the amount of bending of thefloor slab 12 is taken to be X, and the amount of displacement in thehorizontal direction of the pin 21 is taken to be βX, by constructing anamplification mechanism with the first link pieces 15 and second linkpieces 16, ‘β>>1’, and as a result, the amount of operation of thedamping member 18 increases, and by taking the mass of the added mass 25to be m′, then that movement is βm′··X, from lever theory, the inertialforce acting on the floor slab 12 is β2m′··X, and the added mass 25 hasactual motion m′β2, so the mass effect increases.

Also, when the floor slab 12 vibrates upward, movement is in thedirection that will do away with the state of tension of the tensionmembers 14, however, by always having both pins 21 be energized by theenergizing members 17 in the direction toward each other, the state oftension in the tension members 14 described above is maintained.

Therefore, the movement of the first link pieces 15 or the dampingmember 18 is in the opposite direction from the direction describedabove, and by the same amplification mechanism, the damping effect isincreased.

As a result, an effective damping function for vertical vibration, whichis the out-of-plane direction of the floor slab 12, is obtained, andthus it is possible to obtain an elevated isolation function.

The shape and dimensions of the components shown for the embodimentdescribed above are examples, and various modifications are possiblebased on the design requirements.

For example, in the embodiment described above, an example was given ofconstructing the tension member 14 with rope, however, instead of this,it is also possible to construct it using a plurality of steel rods 14a, 14 b, 14 c as shown in FIG. 4.

Also, an oil damper was shown as an example of the damping member 18,however, instead of this, it is also possible to use a viscoelasticmember or elasto-plastic member.

Also, as shown in FIG. 6, it is also possible to install connection legs22 to the tension member 14, and to connect the ends of the first linkpieces 15 to these connection legs 22 by way of pins 19 such that theycan rotate freely, and it is also possible to install, for example,weights 23 to the pins 21 to increase the inertial mass of the movingparts of the base isolation device 10.

Moreover, it is possible to used an active damper for the dampingelement 18, and as shown in FIG. 7, to install a sensor 24 to the floorslab 12 that detects shaking of the floor slab 12, and further, it ispossible to install a controller 25 that adjusts the opening of avariable orifice based on a detection signal from the sensor 24, andadjust the damping force of the damping member 18 to a proper value byadjusting the opening of the variable orifice with this controller 25according to the amount of shaking detected by the sensor 24.

Also, a displacement sensor that detects the amplitude of vibration ofthe floor slab 12 during vibration, or an acceleration sensor thatdetects the acceleration of shaking of the floor slab 12 can be used asthe sensor 24.

Besides the example of structural members described above, man-madeground such as that of a footbridge, bridge over railway tracks,multi-level parking structure, or elevated walkway is also feasible.

An example was given in which support points 13 were located on thebridge supports 11, however, they could also be located on the floorslab 12, which is the structural member.

This embodiment could also be used as a base isolation device thatsuppresses the vibration in the out-of-plane direction of the structuralmembers of an inclined roof, or the structural-support members of avertically standing glass curtain wall.

On the other hand, the connected state of the first link pieces 15 andsecond link pieces 16, and tension member 14, as well as the position ofthe energizing member 17 and damping member 18 can be changed asappropriate.

For example, as shown in FIG. 8A, construction is also possible in whicha rectangular-shaped frame member 26 as shown in FIG. 9, is placedunderneath the floor slab 12, and this frame member 26 is supported byrunning tension members 14 between each corner of this frame member 26and the bridge supports 11 or floor slab 12, and the end sections of apair of parallel sides of this frame member 26 and the floor slab 12 areconnected by the first link pieces 15 and second link pieces 16, whichare connected such that they can rotate freely, and furthermore, theenergizing members 17 and damping members 18 are located between thepins 21, which make up the connections between the first link pieces 15and the second link pieces 16, and the pins 27, which are located on theparallel sides of the frame member 26 and between the pins 21. It isalso possible to reverse the top and bottom as shown in FIG. 8B.

Here, the pins 21 that connect the first link pieces 15 and second linkpieces 16 are located further on the inside of the frame member 26 thanthe straight lines that connect the pins 19 and pins 20.

Moreover, the energizing members 17 comprise compression springs, and byenergizing both pins 21 with these energizing members 17 in a directionsuch that they move apart from each other, the frame member 26 isenergized downward, and a constant tensile force acts on the tensionmembers 14.

Furthermore, as shown in FIG. 10, construction is also possible in whichpins 20 are located underneath the floor slab 12 and separated by a setspace, the second link pieces 16 are connected to these pins 20 suchthat they can rotate freely, and the first link pieces 15 are connectedto the other end of the second link pieces 16 by way of pins 21 suchthat they can rotate freely, and furthermore the other ends of the firstlink pieces 15 are connected to the ends of a connection link piece 28,which is placed such that it is parallel with the line that connectsboth pins 20, by way of pins 19, the energizing member 17 and dampingmember 18 are located between the pins 21, and the tension members 14running between both ends of the connecting link 28 and the floor slab12 or bridge supports 11.

Here, the pins 21 are located further on the outside than the lines thatconnect the pins 19 and pins 20, and the energizing member 17 comprisesa tension spring, such that by having the energizing member 17 energizethe pins 21 in a direction approaching each other, the connection linkpiece 28 is energized downward and constant tensile force is applied tothe tension members 14.

Also, as shown in FIG. 11, construction is also possible in which thepins 21 are located further on the inside than the lines that connectthe pins 19 and pins 20, and the energizing member 17 is a compressionspring that energizes both pins 21 such that they move apart from eachother.

Also, as shown in FIG. 12, construction is also possible in which thepair of second link pieces 16 shown in the modification of FIG. 10 areconnected by one pin 20, and furthermore, the other ends of the pair offirst link pieces 15, which are connected to the other ends of thesesecond link pieces 16 such that can rotate freely, are connected to thetension member 14 by way of one pin 19.

Also, a damping member 18 and energizing member 17 are placed betweenthe pins 21 that connect the first link pieces 15 and the second linkpieces 16, and in this example, this energizing member 17 is constructedusing a tension spring.

Furthermore, as shown in FIG. 13A, construction is also possible inwhich the other ends of the pair of first link pieces 15 shown in FIG.12 are connected on the inside of the pair of second link pieces 16 bypin 19, which is above both pins 21, and a downward facing connectionrod 29 is connected to this pin 19, and this connecting rod 29 isconnected to the tension member 14.

Also, as shown in FIG. 13B, the energizing member 17 can be placedbetween the pin 20 and the pin 19, or the position of this energizingmember 17 and the damping member 18 could be switched.

Also, the tension member 14 can be connected to the first link pieces15, 15 as shown in FIG. 13C.

Moreover, as shown in FIG. 14, construction is possible in which theother ends of the pair of first link pieces 15 shown in FIG. 13 arelocated further on the outside than the second link pieces 16, and theother ends of these first link pieces 15 and the tension member 14 areconnected by a connection plate 30 shown by the dot dashed line in FIG.14 such that they can rotate freely.

Furthermore, as shown in FIG. 15, this embodiment can be applied to awall structure such as a curtain wall to suppress vibration of thecurtain wall or the like. Also, damping members 17 can be installed asshown in FIG. 16.

In any of these modifications, the same functional effect as theembodiment described above can be obtained.

Furthermore, the case of the floor slab 12 being in a horizontal statewas explained, however, the present invention can all be used as a baseisolation device for suppressing vibration in the out-of-plane directionof structural members of an inclined roof, or the structural-supportmembers of a vertically standing glass curtain wall.

INDUSTRIAL APPLICABILITY

As explained above, with the base isolation device for a structure ofthis present invention, by transmitting vibration in the out-of-planedirection of a structure such as a floor slab directly to a dampingmember, the operation of this damping member is performed, and bymagnifying the vibration in the out-of-plane direction of a structuralmember and transmitting it to the damping member, the amount ofoperation of this damping member is greatly increased, and it absorbsthe energy that accompanies the vibration of the structural member, andthus it is possible to maintain the function of base isolation of thestructural member.

1. A base isolation device for a structure that suppresses vibration inthe out-of-plane direction of a structural member of the structure andcomprising: a tension member which is constructed, in a state oftension, between support points, which are located on said structuralmember and separated by a specified space, and has an overall lengththat is longer than the space between these support points; first linkpieces and second link pieces which become a group, respectively and arelocated at two locations separated by a space in the direction of lengthof said tension member, and each of which is connected together suchthat each can rotate freely, thus forming two sets of connections; andan energizing member and a damping member which are located between saidtwo sets of connections between first link pieces and second linkpieces, respectively; wherein the ends of said first link pieces areconnected to a intermediate part of said tension member such that theycan rotate freely; wherein the ends of said second link pieces areconnected to a intermediate part of said structural member such thatthey can rotate freely; wherein said energizing member keeps tensionapplied to the said tension member by energizing said two connections ina direction such that they approach each other; and wherein said dampingmember absorbs said vibration with said vibration, when said twoconnections carry out relative displacement of said two connections. 2.The base isolation device for a structure of claim 1 wherein mass isadded at the connections between said first link pieces and said secondlink pieces.
 3. The base isolation device for a structure of claim 1wherein said tension member is constructed using rope.
 4. The baseisolation device for a structure of claims 1 wherein said tension memberis constructed using a plurality of steel rods that are connected toeach other such that they can rotate freely.
 5. The base isolationdevice for a structure of claim 1 wherein said damping member is an oildamper.
 6. The base isolation device for a structure of claim 1 whereinsaid damping member is an active damper, and together with locating asensor for detecting shaking on said structural member, a controller isinstalled that adjusts the operation of said active damper based on thedetection signal from the sensor.
 7. The base isolation device for astructure of claim 6 wherein said sensor is an acceleration sensor. 8.The base isolation device for a structure of claim 6 wherein said sensoris a displacement sensor.
 9. The base isolation device for a structureof claim 6 wherein said sensor is a velocity sensor.
 10. The baseisolation device for a structure of claim 1 wherein said damping memberis a viscoelastic member or elasto-plastic member.